In convection-enhanced delivery (CED), drugs are infused locally into tissue through a needle, cannula, or microcatheter inserted into the tissue. Transport of the infused material is dominated by convection, which enhances drug penetration into the target tissue compared with diffusion-mediated delivery or systemic delivery.
CED has emerged as a leading investigational delivery technique for the treatment of several disorders. Clinical trials using existing devices show mixed results and suggest that the outcome of the therapy depends strongly on the extent of penetration and distribution of the drug into the target tissue, which is determined by infusion velocity, the relative rates of convection and elimination during CED, and various properties of the target tissue.
As infusion velocity increases, there can be a tendency for the infused fluid to flow back along the insertion pathway, between the exterior of the microcatheter and the surrounding tissue. Flexible microcatheter designs have been constructed to reduce this backflow of the drug-containing fluid. However, fluid backflow during CED treatment still remains a critical problem in clinical practice. This is particularly true in the case of CED within the brain, as the poroelastic nature of the brain tissue contributes to backflow or reflux. There is therefore a need for improved CED devices, e.g., CED devices that reduce or eliminate backflow of the infused fluid between the exterior of the device and the surrounding tissue.